Plasma arc torches are widely used in the cutting of metallic materials. A plasma arc torch generally includes a torch body, an electrode mounted within the body, a nozzle with a central exit orifice, electrical connections, passages for cooling and arc control fluids, a swirl ring to control the fluid flow patterns, and a power supply. The torch produces a plasma arc, which is a constricted ionized jet of a plasma gas with high temperature and high momentum. Gases used in the torch can be non-reactive or reactive (e.g. argon, nitrogen, oxygen or air).
In operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). The pilot arc ionizes gas passing through the nozzle exit orifice. After the ionized gas reduces the electrical resistance between the electrode and the workpiece sufficiently, the arc transfers from the nozzle to the workpiece. The torch may be operated in this transferred plasma arc mode, which is characterized by the conductive flow of ionized gas from the electrode to the workpiece, for the cutting of the workpiece.